The Gunners face Bayern Munich midweek and must attempt to overhaul a 3-1 aggregate scoreline—which will require winning by three goals at the Allianz Arena—but they will do so without their talisman.
As per the BBC Sport report:
He has some bone bruising. The last time it deteriorated into a stress fracture. That's what we don't want to happen.
We trust people who are specialists in this area. He was out for 17 months and we had to deal with it, we must be able to deal with it for two or three games.
—Arsene Wenger, Arsenal manager
After missing 17 months, Wenger, Arsenal and the fans alike are constantly on a knife-edge when it comes to the Stevenage-born youngster's fitness, fearing another lengthy layoff that could seriously harm their side's chances.
England fans, on the whole, worry, too. Ask any English national who they would pin their hopes on for the next decade and, nine times out of 10, it's going to be Wilshere.
But Roy Hodgson is due to announce his England squad on Thursday, and Wilshere, who is already seen as a key member of the team and perhaps a beacon carrier for the 2014 FIFA World Cup campaign, will not be among the names.
That pressure, whether it's indicted by Hodgson, the FA or the fans, will not make Wenger happy, and the quotes above outline how concerned he is.
Wilshere is the heartbeat of the Gunners' team, and without him, they're visibly weaker in technical and mental aspects of the game.
The midfielder has sustained a pretty regular footballing injury, but because of his checkered past, extreme precautions are being taken. That's the sort of thing that can lead to rustiness and, in turn, re-injury.
Take Darren Bent as a recent example.
He lost his place to Christian Benteke in Aston Villa's squad, and when he does get the chance to prove himself, he over-does it. He's not match fit and at one stage this season limped off after coming on as a substitute 10 minutes previously.
There are so many examples of players unable to fulfill their sky-high potential due to constant injury concerns, and Wenger, of all managers, is one of the most guarded.
This injury, the precautions taken and the general air of fear surrounding it will only repeat themselves every time Jack goes down. That's a worry for everyone, including the effect it has on Wilshere himself.